Top U.S. and South Korean commanders inspected frontline positions within the DMZ amid increased North Korean construction and repeated crossings.
South Korea fired warning shots after North Korean troops crossed the fortified border between the two countries, officials said.
The United Nations Command commemorated the sacrifice of Army Capt. Arthur Bonifas and 1st Lt. Mark Barrett, who were killed in an unprovoked attack 50 years ago in the Korean Demilitarized Zone, in the name of peace and stability.
South Korea has relieved the army commander responsible for the western section of the DMZ after investigations into two recent security lapses.
South Korea nearly shot down a U.S. Marine drone near the inter-Korean border after misidentifying it as a threat, triggering civilian shelter alerts.
The South Korean government has warned that heavy rains may have washed landmines from the DMZ into rivers flowing across the inter-Korean border.
North Korea erecting fences inside the DMZ does not violate the Armistice unless it introduces offensive military capabilities, a senior official said.
The only United Nations Command unit permanently stationed inside the DMZ has a new leader.